// for a given input print sum of its previous three terms
#include<stdio.h>

int sum(int a);

int main(){
    int n;
    scanf("%d",&n);
    printf("n : %d\n",n);
    sum(n);
    
    return 0;
}

int sum(int a){
    int e[a];
    scanf("%d\n",&e[0]);
    scanf("%d\n",&e[1]);
    scanf("%d\n",&e[2]);
    printf("e[0]=%d, e[1]=%d, e[2]=%d \n",e[0],e[1],e[2]);
    for(int i=3;i<(a+1);i++){
        e[i]=e[i-1]+e[i-2]+e[i-3];
    }
    printf("%d",e[a-1]);
    // //Printing the entire array
    // int l=sizeof(e)/sizeof(e[0]);
    // for(int i=0;i<l;i++){
    //     printf("\n%d",e[i]);
    // }
}